The rapidly increasing use of computers and their associated integrated circuits in numerous applications has led to the corresponding increase in the use of leadframes for mounting and interconnecting these circuits for end use application. For example, the use of integrated circuit electronics in automobiles includes audio entertainment systems, air bag sensors and electronic control units.
Automobile engines are subjected to a harsh environment created by high temperature, corrosion, vibration and the like. To accommodate these conditions, and the need for compactness, considerable care must be taken to design and fabricate leadframes which mount electronic integrated circuits and allow for interconnections to be made reliably by a wire bonding operation between the circuit bond pads and external contacts and/or terminals.
Because of the many different integrated circuits that are used today, different designs and configurations for the leadframes must be provided. In one widely used method for fabricating these leadframes, a surface coat of aluminum is applied to a base metal such as brass. This coating, which is typically required in a selective area on an electric component, is produced by electroplating, cladding, welding or other known techniques.
The use of aluminum wire bonding to create the necessary interconnects for external components has become widespread, largely because aluminum is used in the bond pads and leadframes. In a conventional leadframe fabrication, the aluminum is placed into grooves patterned in a base made of brass or other copper alloy metal. The leadframe is then rolled and shaped to its desired thickness and width, after which the aluminum pattern is masked. The unit is then subjected to an electroplating process which deposits tin or tin-lead on all unmasked portions of the leadframe, that is, all portions except where the aluminum is present.
This art-recognized technique for making aluminum in-laid products is relatively expensive because specially designed leadframes and masking operations are required for unique product specifications. These special design features have interfered with the development of a generic or standardized leadframe which can be used for multiple applications, thereby permitting cost-reducing, volume-related manufacturing techniques.
In accordance with this background, a need exists for a versatile leadframe which can be used in different configurations for making wire bond interconnects to hybrid electronic integrated circuitry. There is also a need for a less costly fabrication process which allows a manufacturer to improve quality control and benefit from economies of scale.